Backers and opponents of Egyptian President Mohamed Morsi traded gunfire and threw firecrackers during brutal street fighting in Alexandria Friday.

Riot police moved in with armored vehicles and tear gas, but not before the offices of Mr. Morsi's political party were set on fire.

Authorities say two people have been killed, including a U.S. citizen stabbed to death while taking pictures of the riots. The State Department has issued a travel warning for Egypt, telling Americas to put off non-essential travel there. Some embassy workers and their families will be evacuated.

Protesters are gathering in Cairo's Tahrir Square, waving Egyptian flags and calling for Mr. Morsi's departure. They are preparing for a massive anti-government rally Sunday, the one-year anniversary of Mr. Morsi's presidency.

The opposition accuses Mr. Morsi and his Muslim Brotherhood movement of trying to undermine secular rights and not living up to the 2011 uprising that forced ex-president Hosni Mubarak to flee.

Morsi supporters are also promising to fill the streets, accusing the opposition of plotting a coup.

Egyptian military officials are urging both sides to avoid violence and negotiate. But neither side appears willing to give in.

OPTIONAL SOUNDBITES

SABER ATTA, MORSI SUPPORTER ( in Arabic ))

"Mohamed Morsi will not fall because he has a people who love him and a group who support him. It is impossible and they are wrong to think that one day Morsi will have the same fate as Hosni Mubarak."

AMR MOUSSA, OPPOSITION LEADER

"He should take the voice of the people seriously and the protests, the angry comments, as an expression - major expression - of dissatisfaction. Please take that seriously and accept the early elections."

"They don't want to recognize that there is anger and those are all people who are being pushed and directed by others. And they are missing the point, they are missing a major point in this."